Process for the preparation of hydroxyethylcyclohexanes and hydroxyethylpiperidines

Abstract

Hydroxyethylcyclohexanes which can optionally contain a nitrogen atom in the cyclohexane ring are obtained in a particularly selective manner by catalytic hydrogenation of the corresponding hydroxyethylbenzene or hydroxyethylpyridines when ruthenium which has been treated before use with a reducing agent is used as catalyst.

What is claimed is:  
     
       1. A process for the preparation of a hydroxyethylcyclohexane that contains a nitrogen atom in the cyclohexane ring by catalytic hydrogenation of the corresponding hydroxyethyl pyridine, wherein ruthenium which has been treated before use with a reducing agent is used as catalyst. 
     
     
       2. A process according to claim  1 , wherein a hydroxyethylpyridine of the formula (I)                    
       wherein 
       X is N and  
       R 1  and R 2  independently of one another are each hydrogen, hydroxyl, amino,  
       C 1-C   10 -alkyl, C 3 -C 6 -cycloalkyl, C 6 -C 10 -aryl, C 7 -C 12 -aralkyl, C 1 -C 10 -alkoxy or  
       C 3 -C 6 -cycloalkoxy, is used  
       and a hydroxyethylcyclohexane that contains a nitrogen atom in the cyclohexane ring and corresponds to the formula (II)                    
        wherein  
       Y is NH and  
       R 1  and R 2 are as defined above, is obtained.  
     
     
       3. A process according to claim  1 , wherein the ruthenium catalyst used comprises a metallic ruthenium on a support. 
     
     
       4. A process according to claim  1 , wherein a ruthenium-containing supported catalyst is used which, prior to its use, has been treated with hydrogen or another reducing agent at an elevated temperature. 
     
     
       5. A process according to claim  1 , wherein the pretreatment of the ruthenium is carried out with hydrogen at a temperature ranging from 120 to 250° C. and a pressure ranging from 120 to 250 bar. 
     
     
       6. A process according to claim  1 , wherein a ruthenium-containing supported catalyst which contains, as a support material, charcoals, aluminum oxides or silicas is used. 
     
     
       7. A process according to claim  1 , wherein the process is practiced continuously and from 0.01 to 10% by weight of ruthenium catalyst (taking only Ru metal into account), based on hydroxyethylpyridine used, is used. 
     
     
       8. A process according to claim  1 , wherein the process is carried out in a solvent which is an alkane which has a boiling point above 70° C. at atmospheric pressure. 
     
     
       9. A process according to claim  8 , wherein the alkane used comprises a component selected from the group consisting of isooctane, cyclohexane and methylcyclohexane. 
     
     
       10. A process according to claim  1 , wherein the hydrogenation is carried out at a temperature ranging from 50 to 250° C. and a hydrogen pressure ranging from 5 to 200 bar.